Wireless communication networks enable mobile stations, such as cellular phones, personal digital assistants, and laptop computers, to receive voice and data services. The increased use of the mobile stations has resulted in an increased demand for high-speed, flexible, and reliable wireless communication networks.
Mobile stations operate in either a connected state or an idle state. In the connected state, the mobile station synchronizes with the base station in order to establish a connection with the base station. The base station then communicates with the mobile station over the established connection. However, to conserve battery power, the mobile station may enter into an idle state, in which the mobile station does not establish a connection with a base station.
Moreover, conventional wireless communication networks use unicast transmissions, in which a single base station transmits data to a single mobile station. In order for the mobile station to receive the transmitted data, it must be in the connected state with the base station. Thus, when using unicast transmission, the mobile station cannot receive the transmitted data if it is operating in an idle state.
By contrast, multicast and broadcast services (MBS) enable base station(s) to transmit data to multiple mobile stations at a time, over a coverage area of the base station(s). When using MBS, the mobile station can receive data in both the connected state and in the idle state.
In MBS, the mobile station receives data from a serving base station. In some instances, the mobile station may move out of a coverage area of the serving base station and into a coverage area of a target base station. The mobile station may receive a stronger signal from the target base station, and thus, may need to receive the data from the target base station instead of the serving base station. In this way, the serving base station and the target base station are both base stations that the mobile device interacts with during a handover of service.
The move from the serving base station to the target base station may occur while the mobile station is receiving a service from the serving base station, such as a television program, music, or other streaming content, for example. Thus, the mobile station needs to receive the service from the target base station, at the point at which the received signal strength from the serving base station decreases below a predetermined threshold. To accomplish this, the serving base station “hands-over” the service to the target base station. Unlike unicast services, the handover for MBS can take place when the mobile station is in either a connected state or in an idle state. Moreover, it is desirable that continuity of service is maintained during the handover, so that there is not a gap in the content from the perspective of a user of the mobile station.